DESCRIPTION
The Upper Skagit Knotweed Control Project is an innovative program with a strategic and thoughtful approach to controlling the invasive plant species knotweed in the Upper Skagit watershed that works in a top-down, watershed-scale approach. This project is part of a long-term, basin-wide approach to knotweed control in the Upper Skagit watershed that has been advanced by the Skagit Cooperative Weed Management Area Working Group (Skagit CWMA) since 2001. This watershed-wide effort has been possible due to cooperation and partnership from over 15 organizations as well as more than 100 private landowners. Since the project began in 2001, the effort has achieved 50% control of knotweed in the Upper Skagit and the project is recognized as a model for invasive species work in Washington State. If invasive species such as knotweed are left untreated, healthy riparian areas will be unable to develop and habitat functions will be lost. Knotweed and other non-native invasive plants are detrimental to freshwater ecosystems and natural riparian processes, which in turn negatively impacts fish and wildlife habitats and populations.
The floodplains in the Upper Skagit watershed (including the Sauk, Suiattle and Cascade Rivers) are a high priority area for protection and restoration actions in order to recover critical habitat for threatened Chinook salmon in Puget Sound. There is a coordinated effort to protect floodplain habitat in the Upper Skagit watershed through the members of the Skagit Watershed Council. As part of its role in protecting floodplain properties, TNC completed a Site Conservation Plan in 2001 that identified the primary threats to biodiversity in the Upper Skagit ecosystem. Invasive species were identified as a threat, and in particular, three species of knotweed (Japanese, Giant, and Bohemian) were singled out above other invasive species as posing a significant threat to the Upper Skagit watershed floodplain system.
There are three species of knotweed in the upper Skagit River watershed-Japanese, Giant, and Bohemian knotweed have all been found in the project area since 2001. The extent is limited in that while there is knotweed throughout the most of the basin, there are not areas with large monocultures as seen in other rivers such as the Stillaguamish, Skykomish or Snoqualmie rivers. Also, there are numerous tributaries and segments of the mainstem Skagit and Sauk rivers where knotweed is not present at all.
The invasive, non-native knotweed species have become increasingly common in riparian corridors throughout North America. A recently published University of Washington study investigated the effects of knotweed invasion on the abundance and diversity of native plants as well as the quantity and nutrient quality of leaf-litter inputs in riparian forests in western Washington . The study found that by displacing native species and reducing nutrient quality of litter inputs, knotweed invasion has the potential to cause long-term changes in the structure and functioning of riparian forests and adjacent aquatic habitats.
The Upper Skagit Knotweed Project focuses on the Upper Skagit river basin, approximately 2,960 square miles in size. The project area includes the Skagit and Sauk River floodplains and surrounding uplands from the upper portions of these watersheds to the confluence of the Skagit and Sauk rivers at the town of Rockport. The project area also contains the floodplains of the Cascade and Suiattle Rivers, as well as smaller tributaries of these reaches.